U.S. patent number 6,344,938 [Application Number 09/535,108] was granted by the patent office on 2002-02-05 for method and apparatus for preemptive head crash avoidance in a disk drive.
This patent grant is currently assigned to International Business Machines Corporation. Invention is credited to Gordon James Smith.
United States Patent |
6,344,938 |
Smith |
February 5, 2002 |
**Please see images for:
( Certificate of Correction ) ** |
Method and apparatus for preemptive head crash avoidance in a disk
drive
Abstract
A method and apparatus are provided for preemptive head crash
avoidance in a direct access storage device (DASD). At least two
actuators are provided in the DASD. Each actuator services at least
one transducer head. Monitoring for a predicted head crash is
performed. Responsive to an identified predicted head crash, a
transducer head for the predicted head crash is unloaded and
unloading each additional transducer head being serviced by an
actuator for the transducer head for the predicted head crash. A
data backup process is performed. Responsive to an identified
predicted head crash, data are transferred from a disk surface
associated with the transducer head for the predicted head crash
and transferring data from each disk surface associated with each
additional transducer head being serviced by the actuator for the
transducer head for the predicted head crash.
Inventors: |
Smith; Gordon James (Rochester,
MN) |
Assignee: |
International Business Machines
Corporation (Armonk, NY)
|
Family
ID: |
24132876 |
Appl.
No.: |
09/535,108 |
Filed: |
March 24, 2000 |
Current U.S.
Class: |
360/25; 360/31;
360/47; 360/60; 360/75; G9B/21.026; G9B/5.181 |
Current CPC
Class: |
G11B
5/54 (20130101); G11B 21/21 (20130101); G11B
5/012 (20130101) |
Current International
Class: |
G11B
21/21 (20060101); G11B 5/54 (20060101); G11B
5/012 (20060101); G11B 005/02 () |
Field of
Search: |
;360/25,31,75,53,47,60
;324/212,226 ;714/6,769,770 ;711/111,112,114
;369/53.1,53.42,53.45 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Faber; Alan T.
Attorney, Agent or Firm: Pennington; Joan
Claims
What is claimed is:
1. A method for preemptive head crash avoidance in a direct access
storage device (DASD) comprising the steps of:
utilizing at least two actuators, each said actuator servicing at
least one transducer head;
monitoring for a predicted head crash; and
responsive to an identified predicted head crash, unloading a
transducer head for said predicted head crash and unloading each
additional transducer head being serviced by an actuator for said
transducer head for said predicted head crash.
2. A method for preemptive head crash avoidance in a direct access
storage device (DASD) as recited in claim 1 further includes the
steps of responsive to an identified predicted head crash,
transferring data from a disk surface associated with said
transducer head for said predicted head crash and transferring data
from a disk surface associated with each additional transducer head
being serviced by said actuator for said transducer head for said
predicted head crash.
3. A method for preemptive head crash avoidance in a direct access
storage device (DASD) as recited in claim 2 wherein the steps of
transferring data includes the step of transferring data to a disk
surface addressed by a different one of said at least two actuators
than said actuator for said transducer head for said predicted head
crash.
4. A method for preemptive head crash avoidance in a direct access
storage device (DASD) as recited in claim 2 includes the steps of
checking a functionality of said transducer head for said predicted
head crash and stopping data transfer responsive to an identified
predefined functionality of said transducer head for said predicted
head crash.
5. A method for preemptive head crash avoidance in a direct access
storage device (DASD) as recited in claim 2 wherein the steps of
responsive to an identified predicted head crash, transferring data
from a disk surface associated with said transducer head for said
predicted head crash and transferring data from a disk surface
associated with each additional transducer head being serviced by
said actuator for said transducer head for said predicted head
crash includes the step of identifying a data hierarchy for
transferring said data.
6. A method for preemptive head crash avoidance in a direct access
storage device (DASD) as recited in claim 7 further includes the
steps of utilizing a different one of said at least two actuators
than said actuator for said transducer head for said predicted head
crash and continuing operation of the direct access storage device
(DASD).
7. A computer program product for preemptive head crash avoidance
in a direct access storage device (DASD), said computer program
product including a plurality of computer executable instructions
stored on a computer readable medium, wherein said instructions,
when executed by said DASD, cause the DASD to perform the steps
of:
monitoring for a predicted head crash; responsive to an identified
predicted head crash, transferring data from a disk surface
associated with a transducer head for said predicted head crash and
transferring data from each disk surface associated with each
additional transducer head being serviced by said actuator for said
transducer head for said predicted head crash; and
responsive to an identified predicted head crash, unloading a
transducer head for said predicted head crash and unloading each
additional transducer head being serviced by an actuator for said
transducer head for said predicted head crash.
8. A computer program product for preemptive head crash avoidance
in a direct access storage device (DASD) as recited in claim 7
where in the steps of transferring data includes the step of
transferring data to a disk surface addressed by a different
actuator than said actuator for said transducer head for said
predicted head crash.
9. A computer program product for preemptive head crash avoidance
in a direct access storage device (DASD) as recited in claim 7
wherein the steps of transferring data includes the step of
identifying a data hierarchy for transferring said data.
10. A computer program product for preemptive head crash avoidance
in a direct access storage device (DASD) as recited in claim 7
further includes the steps of utilizing a different actuator than
said actuator for said transducer head for said predicted head
crash and continuing operation of the direct access storage device
(DASD).
11. Apparatus for preemptive head crash avoidance in a direct
access storage device (DASD) comprising:
at least two actuators, each said actuator respectively servicing
at least one transducer head;
a control unit, said control unit for monitoring for a predicted
head crash;
said control unit, responsive to an identified predicted head
crash, for transferring data from a disk surface associated with a
transducer head for said predicted head crash and for transferring
data from each disk surface associated with each additional
transducer head being serviced by said actuator for said transducer
head for said predicted head crash; and
said control unit, responsive to an identified predicted head
crash, for unloading a transducer head for said predicted head
crash and for unloading each additional transducer head being
serviced by an actuator for said transducer head for said predicted
head crash.
12. Apparatus for preemptive head crash avoidance in a direct
access storage device (DASD) as recited in claim 11 wherein said
control unit, responsive to unloading said transducer heads, for
utilizing a different actuator than said actuator for said
transducer head for said predicted head crash and continuing
operation of the direct access storage device (DASD).
13. Apparatus for preemptive head crash avoidance in a direct
access storage device (DASD) as recited in claim 11 wherein said
control unit, for identifying a data hierarchy for transferring
said data and for transferring data to a disk surface addressed by
a different actuator than said actuator for said transducer head
for said predicted head crash.
Description
FIELD OF THE INVENTION
The present invention relates generally to the data processing
field, and more particularly, relates to a method and apparatus for
preemptive head crash avoidance in a direct access storage device
(DASD).
DESCRIPTION OF THE RELATED ART
Computers often include auxiliary memory storage units having media
on which data can be written and from which data can be read for
later use. Disk drive units incorporating stacked, commonly rotated
rigid magnetic disks are used for storage of data in magnetic form
on the disk surfaces. Data is recorded in concentric, radially
spaced data information tracks arrayed on the surfaces of the
disks. Transducer heads driven in a path toward and away from the
drive axis write data to the disks and read data from the
disks.
Data located on a particular track on a disk surface is read or
written by properly positioning a data transducer head directly
over the track. In order to maintain the head in proper position
over the data track, track-following servo systems often are
incorporated into disk drives. Servo position control is used to
position the data heads in registration with the data information
tracks. A sector servo system uses the data heads as servo
transducers in a time multiplexed fashion. As a head is following a
particular track on a rotating disk, the head will pick up data
information and servo information alternately. Servo information,
interlaced with data information, is prewritten on the disk
surfaces at manufacturing time within narrow radial sectors as
spokes on a wagon wheel. A servo system that interlaces data and
servo information is commonly referred to as sector servo or
embedded servo. Another servo system uses a dedicated servo
transducer head to read position signals recorded in servo
information tracks on a dedicated disk surface. The data heads are
ganged with the servo head for simultaneous movement relative to
the data information tracks and the servo information tracks. To
access the disk drive unit, a feedback sector servo controlled
drive system locates the head in a desired position, where data is
to be written or read.
A head crash often renders a conventional disk drive inoperable.
One of the reasons for magnetic recording heads crashing of a disk
surface, for example, causing catastrophic failure is the presence
of protruding disk defects or asperities. The manufacturing glide
test screens disk drives for unacceptable disk asperities in order
to reduce the probability of a crash. Some of the disk defects
also, are grown during the life of the drive. These defects include
ding marks, pits, gouges, protruding disk defects or thermal
asperities. Large surface bumps are notorious for causing physical
head-to-disk contact, which is the precursor for a fatal disk
crash. All users of hard disk drives dread even the thought of a
fatal disk crash, since all data stored on that unfortunate disk
drive may be lost forever.
A need exists for a method and apparatus for preemptive head crash
avoidance in a direct access storage device (DASD).
SUMMARY OF THE INVENTION
A principal object of the present invention is to provide a method
and apparatus for preemptive head crash avoidance in a direct
access storage device (DASD). Other important objects of the
present invention are to provide such method and apparatus for
preemptive head crash avoidance in a direct access storage device
(DASD) substantially without negative effect; and that overcome
many of the disadvantages of prior art arrangements.
In brief, a method and apparatus are provided for preemptive head
crash avoidance in a direct access storage device (DASD). At least
two actuators are provided in the DASD. Each actuator services at
least one transducer head. Monitoring for a predicted head crash is
performed. Responsive to an identified predicted head crash, a
transducer head for the predicted head crash is unloaded and
unloading each additional transducer head being serviced by an
actuator for the transducer head for the predicted head crash.
In accordance with features of the invention, a data backup process
is performed. Responsive to an identified predicted head crash,
data are transferred from a disk surface associated with the
transducer head for the predicted head crash and transferring data
from each disk surface associated with each additional transducer
head being serviced by the actuator for the transducer head for the
predicted head crash.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention together with the above and other objects and
advantages may best be understood from the following detailed
description of the preferred embodiments of the invention
illustrated in the drawings, wherein:
FIG. 1 is a schematic and block diagram representation illustrating
a direct access storage device (DASD) for implementing methods for
preemptive head crash avoidance in accordance with the preferred
embodiment;
FIGS. 2 and 3 are diagrams similar to FIG. 1 illustrating exemplary
sequential steps for preemptive head crash avoidance in accordance
with the preferred embodiment;
FIG. 4 is a flow chart illustrating sequential steps for preemptive
head crash avoidance in accordance with the preferred embodiment;
and
FIG. 5 is a block diagram illustrating a computer program product
in accordance with the preferred embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Having reference now to the drawings, in FIG. 1 there is
illustrated a direct access data storage device (DASD) generally
designated as 100 including a stack 102 of disks 104A and 104B each
having at least one magnetic surface 106. The disks 104A and 104B
are mounted parallel to one another for simultaneous rotation on
and by an integrated spindle and motor assembly 108. Information on
each magnetic disk surface 106 is read from or written to the disk
surface 106 by a corresponding transducer head assembly 110 movable
in a path having a radial component across the rotating disk
surface 106.
Each transducer head assembly 110 is carried by an arm 112A, 112B.
The arms 112A, 112B are ganged together for simultaneous pivotal
movement by a respective voice coil motor (VCM) magnet assembly or
actuator 114A, 114B. Drive signals applied to the VCM magnet
assembly 114A, 114B cause the corresponding arms 112A, 112B to move
in unison to position the transducer head assemblies 110 in
registration with information storage tracks on the disk surfaces
106 where information is written or read. A control unit 116 that
generates signals controlling the operation of various components
of the DASD.
In accordance with features of the preferred embodiment, monitoring
is performed to determine if a head is about to crash. When a head
crash is predicted, data residing on the disk surfaces 106 serviced
by the same actuator comb 114A or 114B containing the pre-crashed
head 110 is backed up as required on the remaining disks in the
DASD 100. The pre-crashed head 110 and other heads 110 serviced by
the same actuator comb 114A or 114B are unloaded. By unloading the
offending head 110, the DASD 100 can return to normal operation at
a reduced capacity. If the head 110 is already crashing the
actuator 114A, 114B containing this head is unloaded and data
backup may be avoided. After heads 110 are unloaded, the remaining
actuator 114A or 114B can continue normal operations.
Control unit 116 is suitably programmed to execute the logical flow
functions of FIG. 4 of the preferred embodiment and as illustrated
in FIGS. 1, 2, and 3.
As shown in FIG. 1, DASD 100 includes at least two actuators or a
split actuator 114A, 114B. One of the heads 110 moved by actuator
114A is predicted to crash.
Referring to FIG. 2, as indicated by multiple arrows labeled A,
data is moved from the disk surfaces 106 serviced by the actuator
114A to the remaining disk surfaces 106 serviced by the actuator
114B.
Referring to FIG. 3, the crashing head 110 and other heads 110 on
the same actuator 114A are unloaded. After heads 110 serviced by
actuator 114A are unloaded, the remaining actuator 114B can
continue normal operations.
Referring to FIG. 4, there is shown a flow chart illustrating
exemplary sequential steps for preemptive head crash avoidance in
accordance with the preferred embodiment. The sequential operations
start as indicated in a block 400. Monitoring for a predicted head
crash is performed as indicated in a decision block 402. Methods
such as flying height or error/reassign rate monitoring are used to
make this assessment at decision block 402. When a predicted head
crash is not identified, then after a set delay as indicated in a
block 404, monitoring for a predicted head crash is continued at
decision block 402. When determined that a head crash is predicted
at decision block 402, then data from the affected disks are moved
to disks serviced by another actuator as indicated in a block 406.
A file allocation table or other means of determining disk drive
directory information is used to determine a hierarch so that the
most important data is moved to the disk surfaces 106 addressed by
the operating actuator 114A, 114B. For example, the most important
data is the data that cannot be rebuilt from another source, such
as a CD ROM, tape, or the Internet. While the data is being
transferred at block 406, the functionality of the crashing head is
periodically checked. If the pending crash has progressed, then the
actuator 114A, 114B can unload the heads immediately and preempt
the data backup process. After the data backup process is completed
or preempted at block 406, then the crashing head and other heads
110 on the same actuator 114A or 114B are unloaded as indicated in
a block 408. This completes the sequential operations as indicated
in a block 410.
It should be understood that the data from the affected disks can
be moved to a separate storage device, such as another disk
drive.
Referring now to FIG. 5, an article of manufacture or a computer
program product 500 of the invention is illustrated. The computer
program product 500 includes a recording medium 502, such as, a
floppy disk, a high capacity read only memory in the form of an
optically read compact disk or CD-ROM, a tape, a transmission type
media such as a digital or analog communications link, or a similar
computer program product. Recording medium 502 stores program means
504, 506, 508, 510 on the medium 502 for carrying out the methods
for preemptive head crash avoidance of the preferred embodiment in
the DASD 100 of FIG. 1.
A sequence of program instructions or a logical assembly of one or
more interrelated modules defined by the recorded program means
504, 506, 508, 510, direct the DASD 100 for implementing preemptive
head crash avoidance of the preferred embodiment.
While the present invention has been described with reference to
the details of the embodiments of the invention shown in the
drawing, these details are not intended to limit the scope of the
invention as claimed in the appended claims.
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